/*
 *  Copyright 2008-2009 NVIDIA Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */


#include <cusp/array1d.h>
#include <cusp/blas.h>
#include <cusp/multiply.h>
#include <cusp/monitor.h>
#include <cusp/linear_operator.h>

namespace blas = cusp::blas;

namespace cusp
{

template <class LinearOperator,
          class Vector>
void richardson(LinearOperator& A,
                Vector& x,
                Vector& b)
{
    typedef typename LinearOperator::value_type   ValueType;

    cusp::default_monitor<ValueType> monitor(b);

    cusp::richardson(A, x, b, monitor);
}

template <class LinearOperator,
          class Vector,
          class Monitor>
void richardson(LinearOperator& A,
                Vector& x,
                Vector& b,
                Monitor& monitor)
{
    typedef typename LinearOperator::value_type   ValueType;
    typedef typename LinearOperator::memory_space MemorySpace;

    cusp::identity_operator<ValueType,MemorySpace> M(A.num_rows, A.num_cols);

    cusp::richardson(A, x, b, monitor, M);
}

template <class LinearOperator,
          class Vector,
          class Monitor,
          class Preconditioner>
void richardson(LinearOperator& A,
                Vector& x,
                Vector& b,
                Monitor& monitor,
                Preconditioner& M)
{
    CUSP_PROFILE_SCOPED();

    typedef typename LinearOperator::value_type   ValueType;
    typedef typename LinearOperator::memory_space MemorySpace;

    assert(A.num_rows == A.num_cols);        // sanity check

    const size_t N = A.num_rows;

    // allocate workspace
    cusp::array1d<ValueType,MemorySpace> r(N);
    cusp::array1d<ValueType,MemorySpace> d(N);
        
    // residue r = A * x - b
    cusp::multiply(A, x, r);
    blas::axpy(b, r, ValueType(-1));

    // preconditioned residue
    cusp::multiply(M, r, d);

    // loop
    while (!monitor.finished(r))
    {
        // x^(k+1) = x^(k) - d
        blas::axpy(d, x, ValueType(-1));
        
        // residue r = A * x - b
        cusp::multiply(A, x, r);
        blas::axpy(b, r, ValueType(-1));

        // preconditioned residue
        cusp::multiply(M, r, d);

        ++monitor;
    }
}

} // end namespace cusp

